Sauté the onion and garlic in the oil in a heavy saucepan until the onions turn golden in colour. Add the lentils and stock, lemon zest, ground pepper and simmer, uncovered over a low heat until the lentils are tender (about 40 minutes).Add the chickpeas, cumin, mint, parsley and cook for 10 more minutes.Remove from the heat, stir in lemon juice and coriander.Add salt to taste and serve.Serves 6.